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Gastrointestinal Carcinoid Tumors

General Information About Gastrointestinal Carcinoid Tumors

Epidemiology

The age-adjusted incidence of carcinoid tumors worldwide is approximately 2 per 100,000 persons.[1,2] The average age at diagnosis is 61.4 years.[3] Carcinoid tumors represent about 0.5% of all newly diagnosed malignancies.[2,3]

Anatomy

Carcinoid tumors are rare, slow-growing tumors that originate in cells of the diffuse neuroendocrine system. They occur most frequently in tissues derived from the embryonic gut. Foregut tumors, which account for up to 25% of cases, arise in the lung, thymus, stomach, or proximal duodenum. Midgut tumors, which account for up to 50% of cases, arise in the small intestine, appendix, or proximal colon, with the appendix being the most common site of origin. Hindgut tumors, which account for approximately 15% of cases, arise in the distal colon or rectum.[4] Other sites of origin include the gallbladder, kidney, liver, pancreas, ovary, and testis.[3,4,5]

Gastrointestinal (GI) carcinoid tumors, especially tumors of the small intestine, are often associated with other cancers. Synchronous or metachronous cancers occur in approximately 29% of patients with small intestinal carcinoids.[3] However, it is possible that the association may be due in part to the serendipitous discovery of slow-growing carcinoid tumors, which are found while investigating symptoms from, or staging, other tumors.

Histology

The term carcinoid should be used for well-differentiated neuroendocrine tumors (NETs) or carcinomas of the GI tract only; the term should not be used to describe pancreatic NETs or islet cell tumors.[6] (Refer to the PDQ summary on Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) for more information.) Data regarding carcinoids and other NETs, such as poorly differentiated neuroendocrine carcinomas, may be combined in some epidemiologic and clinical studies, rendering separate consideration difficult. Occurring nonrandomly throughout the GI tract are more than 14 cell types, which produce different hormones.[7] (Refer to the Cellular and Pathologic Classification of Gastrointestinal Carcinoid Tumors section of this summary for more information.) Although the cellular origin of NETs of the GI tract is uncertain, consistent expression of cytokeratins in NETs and the expression of the caudal-related homeodomain protein 2 (CdX2 protein), an intestinal transcription factor in endocrine tumors of the small intestine, suggests an origin from an epithelial precursor cell.[8]

Most NETs of the small and large intestines occur sporadically, while others may occur within the background of an inherited neoplasia syndrome such as multiple endocrine neoplasia type 1 (MEN1) or neurofibromatosis type 1 (NF1) (e.g., gastrin-producing G-cell tumors and somatostatin-producing D-cell tumors of the duodenum, respectively).[9] Tumor multifocality is the rule within the background of neuroendocrine cell hyperplasia, but multifocality is found in approximately one-third of patients with small enterochromaffin cell tumors in the absence of proliferative or genetic factors; clonality studies suggest that most of these neoplasms are separate primary lesions.[10,11] Gastric carcinoids may be associated with chronic atrophic gastritis.[7]

Individual carcinoid tumors have specific histologic and immunohistochemical features based on their anatomic location and endocrine cell type. However, all carcinoids share common pathologic features that characterize them as well-differentiated NETs.[5] In the gastric or intestinal wall, carcinoids may occur as firm white, yellow, or gray nodules and may be intramural masses or may protrude into the lumen as polypoid nodules; the overlying gastric or intestinal mucosa may be intact or have focal ulceration.

Neuroendocrine cells have uniform nuclei and abundant granular or faintly staining (clear) cytoplasm, and are present as solid or small trabecular clusters, or are dispersed among other cells, which may make them difficult to recognize in sections stained with hematoxylin and eosin; immunostaining enables their exact identification.[12] At the ultrastructural level, neuroendocrine cells contain cytoplasmic membrane-bound dense-cored secretory granules (diameter >80 nm) and may also contain small clear vesicles (diameter 40–80 nm) that correspond to the synaptic vesicles of neurons.

Molecular genetics

Occasionally, GI carcinoids occur in association with inherited syndromes, such as MEN1 and NF1.[13,14,15]

MEN1 is caused by alterations of the MEN1 gene located at chromosomal region 11q13. (Refer to the PDQ summary on Genetics of Medullary Thyroid Cancer for more information.) Most carcinoids associated with MEN1 appear to be of foregut origin.[13] NF1 is an autosomal dominant genetic disorder caused by alteration of the NF1 gene at chromosome 17q11.[16] Carcinoids in patients with NF1 appear to arise primarily in the periampullary region.[5,17,18]

In sporadic GI carcinoids, numerous chromosomal imbalances have been found by comparative genome hybridization analysis. Gains involving chromosomes 5, 14, 17 (especially 17q), and 19 and losses involving chromosomes 11 (especially 11q) and 18 appear to be the most common.[19,20]

The most frequently reported mutated gene in GI carcinoids is β-catenin (CTNNB1). In one study, β-catenin exon 3 mutations were found in 27 (37.5%) of 72 cases.[21]

However, no consistent genetic markers for GI carcinoid prognosis have yet been identified.[9] (Refer to the Cellular and Pathologic Classification of Gastrointestinal Carcinoid Tumors section of this summary for more information.)

Carcinoid syndrome

Carcinoid syndrome, which occurs in fewer than 20% of patients with carcinoid tumors, is caused by the release of metabolically undegraded vasoactive amines into the systemic circulation. It is associated with flushing, abdominal pain and diarrhea, bronchoconstriction, and carcinoid heart disease.[22,23] Because vasoactive amines are efficiently metabolized by the liver, carcinoid syndrome rarely occurs in the absence of hepatic metastases. Exceptions include circumstances in which venous blood draining from a tumor enters directly into the systemic circulation (e.g., primary pulmonary or ovarian carcinoids, pelvic or retroperitoneal involvement by metastatic or locally invasive small bowel carcinoids, or extensive bone metastases).

Carcinoid heart disease develops in more than one-third of patients with carcinoid syndrome. Pathologically, the cardiac valves become thickened because of fibrosis, and the tricuspid and pulmonic valves are affected to a greater extent than the mitral and aortic valves. Symptoms include:[22]

Tricuspid and pulmonic regurgitation.

Pulmonary stenosis.

Mitral and aortic insufficiency.

Cardiac dysrhythmias.

Severe carcinoid heart disease is associated with reduced survival. (Refer to the Prognostic Factors section of this summary for more information.)

Site-Specific Clinical Features

The clinical features of GI carcinoids vary according to anatomical location and cell type.[5,12,24] Most carcinoids in the GI tract are located within 3 feet (~90 cm) of the ileocecal valve, with 50% found in the appendix.[25] They are often detected fortuitously during surgery for another GI disorder or during emergency surgery for appendicitis, GI bleeding, or perforation.[26]

Gastric carcinoids

Most gastric carcinoids are enterochromaffin-like (ECL)-cell carcinoids; rarely, other types may occur in the stomach. (Refer to Table 1 in the Cellular and Pathologic Classification of Gastrointestinal Carcinoid Tumors section of this summary for more information.)

Type I ECL-cell gastric carcinoids, the most common type, typically do not have clinical symptoms. They are often discovered during endoscopy for reflux, anemia, or other reasons; and are typically multifocal. Occurring most commonly in women (female-to-male ratio, 2.5:1) at a mean age of 63 years, achlorhydria may be present, and hypergastrinemia or evidence of antral G-cell hyperplasia is usually found.[5,24,27] These tumors are gastrin-driven and arise in a background of chronic atrophic gastritis of the corpus, usually because of autoimmune pernicious anemia but sometimes caused by Helicobacter pylori infection.[9]

Type II ECL-cell carcinoids, the least common type of gastric carcinoids, occur at a mean age of 50 years with no gender predilection. The hypergastrinemia associated with MEN1-Zollinger-Ellison syndrome (ZES) is thought to promote the ECL-cell hyperplasia that leads to type II tumors.[27,28]

Type I and type II ECL-cell gastric carcinoids have been reported to metastasize in fewer than 10% of cases.[27,29] Type III gastric ECL-cell carcinoids, the second most common type of gastric carcinoid, occur mostly in men (male-to-female ratio, 2.8:1) at a mean age of 55 years.[27] There are no neuroendocrine manifestations, and patients typically present with signs and symptoms related to an aggressive tumor.[5,30]

Duodenal carcinoids

Comprising only 2% to 3% of GI NETs and discovered incidentally or because of symptoms from hormonal or peptide production, duodenal carcinoids may also arise in the periampullary region, obstruct the ampulla of Vater, and produce jaundice.[3,5,31] The age at presentation varies widely (range, 19–90 years; mean age, 53 years).[15,32]

The most common duodenal carcinoids are gastrin-producing G-cell tumors (~two thirds) followed by somatostatin-producing D-cell tumors (~one fifth), which rarely produce systemic manifestations of somatostatin excess.[5,31,33]

Gastrin production from G-cell carcinoids (also called gastrinomas if serum gastrin levels are elevated) results in ZES in approximately one-third of the cases of duodenal G-cell tumors.[24] Although duodenal G-cell carcinoids may occur sporadically, 90% of patients with MEN1 develop them.[5] The clinical manifestations of serum gastrin elevation include:

Nausea.

Vomiting.

Abdominal pain.

Hemorrhage from multiple and recurrent peptic ulcers.

Gastroesophageal reflux caused by excess acid production.

Diarrhea from hypergastrinemia.

The most common symptom is abdominal pain; the combination of abdominal pain and diarrhea is present in approximately 50% of patients. In contrast to sporadic gastrinomas, which are usually solitary lesions, gastrinomas in patients with MEN1-ZES are usually multiple and smaller than 5 mm in size.[5]

Somatostatin-producing D-cell tumors occur exclusively in and around the ampulla of Vater, and as many as 50% of patients with D-cell carcinoids have NF1.[34] Most of the patients with NF1 are black women, and their tumors are exclusively located in the periampullary region.[15,32] As a result of their location, these tumors may cause local obstructive symptoms and signs such as jaundice, pancreatitis, or hemorrhage. Although D-cell carcinoids produce somatostatin, systemic manifestations of excess somatostatin such as steatorrhea, diarrhea, diabetes mellitus, hypochlorhydria and achlorhydria, anemia, and cholelithiasis are rare.[31]

Jejunal and ileal carcinoids

Most jejunal and ileal carcinoids are argentaffin-positive, substance P–containing, and serotonin-producing EC-cell tumors that generate carcinoid syndrome when hepatic or retroperitoneal nodal metastases are present. L-cell, glucagon-like polypeptide-producing, and pancreatic polypeptide- and polypeptide YY-producing tumors occur less frequently.[24] Ileal carcinoids develop preferentially in the terminal ileum.[12] Jejunal and ileal carcinoids occur equally in men and women at a mean age of 65.4 years.[3] Similar to all carcinoids, jejunal and ileal carcinoids vary in their biologic behavior and ability to metastasize. Typically, EC-cell carcinoids of the small intestine metastasize to lymph nodes and the liver.[5] Patients with these lesions may be asymptomatic. The primary tumor may cause small intestinal obstruction, ischemia, or bleeding, and some patients may complain of a long history of intermittent crampy abdominal pain, weight loss, fatigue, abdominal distention, diarrhea, or nausea and vomiting.[5,23,35]

At the time of diagnosis, ileal NETs (i.e., carcinoids plus poorly differentiated neuroendocrine carcinomas) are commonly larger than 2 cm and have metastasized to regional lymph nodes; in as many as 40% of cases, the tumors are multifocal.[12] Immunocytochemically, the cells contain serotonin, substance P, kallikrein, and catecholamine. Approximately 20% of patients with ileal NETs have regional lymph node and liver metastases. Most GI carcinoids secrete their bioactive peptides and amines into the portal circulation, and the effects of these biochemical mediators are diminished or negated by hepatic detoxification; accordingly, carcinoid syndrome (e.g., flush, diarrhea, and endocardial fibrosis) occurs only in patients with liver metastases because hepatic detoxification of serotonin is bypassed.

Appendiceal carcinoids

Most appendiceal carcinoids are serotonin-producing EC-cell tumors similar to carcinoids that occur in the jejunum and ileum; less commonly, appendiceal carcinoids are L-cell tumors similar to those in the colon.[16] The biologic behavior of both cell types is strikingly different in the appendix compared with tumors of the ileum and nonappendiceal colon. Most appendiceal carcinoids have a benign clinical course and do not metastasize, perhaps because growth in the appendix produces obstruction, appendicitis, and subsequent surgical removal.[5,36] Although appendiceal carcinoids occur in patients of all ages, patients with these tumors tend to be much younger than patients diagnosed with other appendiceal neoplasms or carcinoids at other sites. Appendiceal carcinoids are reportedly more common in female patients.[3,5] However, age and gender patterns may be spurious, reflecting the younger age range of patients who typically undergo appendectomy for inflammatory appendicitis, and the larger number of incidental appendectomies performed in women during pelvic operations.

Colorectal carcinoids

Most colorectal carcinoids occur in the rectum; fewer arise in the cecum.[5] In the cecum, argentaffinic EC-cell carcinoids are most common, become increasingly less common in the more distal colon, and are uncommon in the rectum.[31] Rectal carcinoids account for approximately one-fourth of GI carcinoids and fewer than 1% of all rectal cancers.[3,31] Most rectal carcinoids have L-cell differentiation. The mean age of patients at diagnosis for colonic carcinoids is 66 years and for rectal carcinoids, 56.2 years. Although there is no specific gender predilection for colorectal carcinoids, rectal carcinoids are more common in the black population.[3,37] Abdominal pain and weight loss are typical symptoms of colonic carcinoids, but more than 50% of patients with rectal carcinoids are asymptomatic, and the tumors are discovered at routine rectal examination or screening endoscopy.[24] Symptoms of rectal carcinoids include bleeding, pain, and constipation. Metastatic disease from colonic carcinoids may produce carcinoid syndrome, whereas metastatic disease from rectal carcinoids is not associated with carcinoid syndrome.[5,38]

Diagnostics: Biochemical Markers, Imaging, and Approach

Biochemical markers

Biochemical investigations in the diagnosis of GI carcinoids include the use of 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) collection, which has a specificity of approximately 88%, although the sensitivity is reported to be as low as 35%.[39,40,41] A time-consuming test, 5-HIAA requires dietary avoidance of serotonin-rich foods, such as bananas, tomatoes, and eggplant.[42] Measurement of plasma chromogranin A (CgA), first described in a study of adrenal gland secretions in 1967 as one of the soluble protein fractions (also including CgB and CgC) of chromaffin granules, is also useful.[43] Although plasma levels of CgA are very sensitive markers of carcinoids, they are nonspecific because they are also elevated in other types of NETs, such as pancreatic and small cell lung carcinomas.[44,45,46] Plasma CgA appears to be a better biochemical marker of carcinoids than does urinary 5-HIAA.[47] Numerous investigations have revealed an association between plasma CgA levels and disease severity.[26] However, false-positive plasma levels of CgA may occur in patients on proton pump inhibitors, reported to occur even with short-term, low-dose treatment.[48,49] Many other biochemical markers are associated with NETs—including substance P, neurotensin, bradykinin, human chorionic gonadotropin, neuropeptide L, and pancreatic polypeptide—but none match the specificity or predictive value of 5-HIAA or CgA.[44]

There are five different somatostatin receptor (SSTR) subtypes; more than 70% of NETs of both the GI tract and pancreas express multiple subtypes, with a predominance of receptor subtype 2 [sst(2)] and receptor subtype 5 [sst(5)].[50,51] The synthetic radiolabeled SSTR analog 111In-DTP-d-Phe10-{octreotide} affords an important method, somatostatin receptor scintigraphy (SRS), to localize carcinoid tumors, especially sst(2)-positive and sst(5)-positive tumors; imaging is accomplished in one session, and small primary tumors and metastases are diagnosed more readily than with conventional imaging or imaging techniques requiring multiple sessions.[26,52,53] Overall sensitivity of the octreotide scan is reported to be as high as 90%; however, failed detection may result from various technical issues, small tumor size, or inadequate expression of SSTRs.[26,54]

Bone scintigraphy

Bone scintigraphy with 99mTcMDP is the primary imaging modality for identifying bone involvement in NETs and detection rates are reported to be 90% or higher.[26] 123I-MIBG is concentrated by carcinoid tumors in as many as 70% of cases using the same mechanism as norepinephrine and is used successfully to visualize carcinoids; however, 123I-MIBG appears to be about half as sensitive as 111In-octreotide scintigraphy in detecting tumors.[26,55]

CT/MRI

CT and MRI are important modalities used in the initial localization of carcinoid primaries and/or metastases. The median detection rate and sensitivity of CT and/or MRI have been estimated at 80%; detection rates by CT alone vary between 76% and 100%, while MRI detection rates vary between 67% and 100%.[26] CT and MRI may be used for initial localization of the tumor only because both imaging techniques may miss lesions otherwise detected by 111In-octreotide scintigraphy; one study has shown that lesions in 50% of patients were missed, especially in lymph nodes and extrahepatic locations.[26,56]

PET

A promising approach for PET as an imaging modality to visualize GI carcinoids appears to be the use of the radioactive-labeled serotonin precursor 11C-5-hydroxytryptophan (11C-5-HTP). With 11C-5-HTP, tumor detection rates have been reported to be as high as 100%, and some investigators have concluded that 11C-5-HTP PET should be used as a universal detection method for detecting NETs.[57,58,59] In one study of NETS, including 18 patients with GI carcinoids, 11C-5-HTP PET detected tumor lesions in 95% of patients. In 58% of cases, 11C-5-HTP PET detected more lesions than SRS and CT, compared to the 7% that 11C-5-HTP PET did not detect.[59] Other imaging approaches have been investigated using technetium-labeled isotopes, combining CT/MRI with 18F-DOPA PET, combining 131 MIBG with 111In-octreotide, and coupling the isotopes 68Ga and 64Cu to octreotide.[26]

EUS

EUS may be a sensitive method for the detection of gastric and duodenal carcinoids and may be superior to conventional ultrasound, particularly in the detection of small tumors (2mm–3 mm) that are localized in the bowel lumen.[60,61] In one study, the EUS was reported to have an accuracy of 90% for the localization and staging of colorectal carcinoids.[62]

CE

The development of CE in the diagnosis of GI carcinoids is nascent, although this technique may prove useful in the detection of small bowel carcinoids.[63]

Enteroscopy

Double-balloon enteroscopy is a time-consuming procedure that is being studied in the diagnosis of small bowel tumors, including carcinoids.[64,65] It is usually performed under general anesthesia, although it can be done under conscious sedation.

Angiography

MRI angiography has replaced angiography to a large extent. However, selective and supraselective angiography may be useful to:

Demonstrate the degree of tumor vascularity.

Identify the sources of vascular supply.

Delineate the relationship of the tumor to adjacent major vascular structures.

Provide information regarding vascular invasion.

Angiography may be useful as an adjunct to surgery, particularly in the case of large invasive lesions in proximity to the portal vein and superior mesenteric artery. Overall, this imaging technique provides a more precise topographic delineation of the tumor or tumor-related vessels and facilitates resection.[26]

General diagnostic approaches

As might be expected, diagnostic approaches to GI carcinoids vary according to anatomical location. In 2004, a consensus statement regarding the diagnosis and treatment of GI NETs was published on behalf of the European Neuroendocrine Tumor Society,[66] which details site-specific approaches to the diagnosis of GI carcinoids.

Prognostic Factors

Factors that determine the clinical course and outcome of patients with GI carcinoid tumors are complex and multifaceted and include the following:[67]

The site of origin.

The size of the primary tumor.

The anatomical extent of disease.

Elevated expression of the proliferation antigen Ki-67 and the tumor suppressor protein p53 have been associated with poorer prognosis; however, some investigators suggest that the Ki-67 index may be helpful in establishing prognosis of gastric lesions only and maintain that no consistent genetic markers of prognosis have yet been discovered.[9] Adverse clinical prognostic indicators include:

Carcinoid syndrome.

Carcinoid heart disease.

High concentrations of the tumor markers urinary 5-HIAA and plasma chromogranin A.

In general, patients with carcinoid tumors of the appendix and rectum experience longer survival than patients with tumors arising from the stomach, small intestine, and colon. Carcinoid tumors occurring in the small intestine, even those of small size, have a greater propensity to metastasize than those in the appendix, colon, and rectum.[67] Appendiceal and rectal carcinoids are usually small at the time of initial detection, and have rarely metastasized. The presence of metastases has been associated with a reduction in 5-year survival ranging from 39% to 60% in several case series and reviews.[3,68,69,70,71] However, some patients with metastatic carcinoid tumors have an indolent clinical course with survival of several years, whereas others experience an aggressively malignant course with short survival. Although metastases are associated with a shorter survival in large patient samples, the presence of metastases alone does not sufficiently predict the clinical course of the individual patient.

Approximately 35% of carcinoids of the small intestine are associated with carcinoid syndrome. The relatively common carcinoids of the appendix and rectum rarely produce this syndrome, and carcinoids from other sites have intermediate risks.[71,72] Investigations using echocardiographic criteria for carcinoid heart disease found prevalences ranging from 35% to 77% among patients with carcinoid syndrome.[73,74,75,76,77] The tricuspid valve is affected more frequently and severely than the pulmonic valve, and the presence and severity of carcinoid heart disease, particularly tricuspid valve dysfunction, is associated with shortened survival.[74,76,77,78] One study involving 64 patients with midgut carcinoid syndrome found 5-year survival rates of 30% for those with severe carcinoid heart disease versus 75% for those with no cardiac disease.[76]

In another study, statistically significantly reduced survival was observed for patients with midgut carcinoids who had urinary 5-HIAA concentrations greater than 300 μmol/24 hours compared with patients who had lower concentrations of urinary 5-HIAA.[79] Correspondingly, a study of patients with midgut carcinoid syndrome showed that urinary 5-HIAA levels greater than 500 μmol/24 hours were associated with shorter survival.[76] The degree of elevation of urinary 5-HIAA is also associated with the severity of carcinoid symptoms, with the highest levels being observed in patients with carcinoid heart failure.[76,80] In one study, vascular endothelial growth factor (VEGF) expression by low-grade tumors and surrounding stromal cells was associated with progression-free survival (PFS); median durations of PFS in patients with strong and weak VEGF expression were 29 months and 81 months, respectively.[81]

Related Summaries

Other PDQ summaries containing information related to GI carcinoid tumors include the following:

A variety of neuroendocrine cells normally populate the gastrointestinal (GI) mucosa and submucosa. The type, location, and secretory products of GI neuroendocrine cells are well defined and are summarized in Table 1 below. As previously noted, individual carcinoid tumors have specific histologic and immunohistochemical features based on their anatomic location and neuroendocrine cell type. However, all carcinoids share common pathologic features that characterize them as well-differentiated neuroendocrine tumors (NETs).[1]

Updated in 2000, the World Health Organization (WHO) classification of GI NETs is clinically and prognostically useful for patients with newly diagnosed NETs of the GI tract because it accounts for specific biological behavior according to location and tumor differentiation.[4,5]

Well-differentiated carcinomas with a low malignant potential and a favorable prognosis.

Poorly differentiated carcinomas (small cell and fewer large cell), which are highly malignant and carry a poor prognosis.

In this classification, the term carcinoid (or typical carcinoid) is used only for well-differentiated NETs of the GI tract, excluding the pancreas; the term malignant carcinoid (or atypical carcinoid) is used for the corresponding well-differentiated NETs at the same GI tract locations.[6,7] Despite some uncertainty surrounding the role of cell proliferation indices in the prognosis of NETs, it is clear that poorly differentiated carcinomas are highly aggressive and require a special therapeutic approach.[7,8,9] In a second step, the WHO classification subdivides GI NETs on the basis of localization and biology to achieve a prognostically relevant classification of the tumors.[5,6,7,9] In this subclassification, GI anatomical locations included the following:

Stomach (four different types).

Duodenum (and proximal jejunum) (five different types).

Ileum (including the distal jejunum).

Appendix.

Colon-rectum.

(Refer to the Site-Specific Clinical Features section in the General Information About Gastrointestinal Carcinoid Tumors section of this summary for more information about a clinicopathologic correlation of cell types and anatomical location.)

In addition, in the WHO classification scheme, GI NETs have been grouped with pancreatic NETS (islet cell tumors) and labeled as gastroenteropancreatic NETs (GEP-NETs). However, because of differences in chromosomal alteration patterns and molecular genetics between GI NETs and pancreatic NETs, some investigators have suggested that this GEP-NET grouping requires reassessment.[7,9,10]

Because there were no proven molecular and genetic alterations with clinical and prognostic relevance, only traditional morphologic and histopathologic criteria were used in the classification. In addition to the level of differentiation, these criteria include the following:

Traditional cytologic and histopathologic assessment of growth patterns and cellular features of well-differentiated NETs are often of little help in predicting their functional behavior and degree of malignancy. In general, typical carcinoids occurring in the stomach, the appendix, or the rectum have an excellent prognosis.[6] In contrast, poorly differentiated NETs that are composed of cells displaying severe nuclear atypia, a high mitotic index, and few secretory granules are invariably high-grade malignancies.[7]

Diagnostic markers that help to identify GI NETs include the following:

Tumor invades through the muscularis propria into subserosal tissue without penetration of overlying serosa (jejunal or ileal tumors) or invades pancreas or retroperitoneum (ampullary or duodenal tumors) or into nonperitonealized tissues.

A new classification is added for carcinoid tumors that were not classified previously by TNM. This is a new classification. There are substantial differences between the classification schemes of appendiceal carcinomas and carcinoids and between appendiceal carcinoids and other well-differentiated gastrointestinal neuroendocrine tumors (carcinoids).[2]

Serum chromogranin A is identified as a significant prognostic factor.[2]

Table 12. Primary Tumor (T)a,b

b Tumor that is adherent to other organs or structures, grossly, is classified cT4. However, if no tumor is present in the adhesion, microscopically, the classification should be classified pT1–3 depending on the anatomical depth of wall invasion.

c Penetration of the mesoappendix does not seem to be as important a prognostic factor as the size of the primary tumor and is not separately categorized.

pTNM Pathologic Classification. The pT, pN, and pM categories correspond to the T, N, and M categories except that pM0 does not exist as a category.[2]

pN0. Histological examination of a regional lymphadenectomy specimen will ordinarily include 12 or more lymph nodes. If the lymph nodes are negative, but the number ordinarily examined is not met, classify as pN0.[2]

Carcinoid. Histologic grading is not carried out for carcinoid tumors, but a mitotic count of 2–10 per 10 hpf and/or focal necrosis are features of atypical carcinoids (well-differentiated neuroendocrine carcinomas), a type seen much more commonly in the lung than in the appendix.[2]

Goblet cell carcinoids are classified according to the carcinoma scheme.[2]

This staging classification applies to carcinoids that arise in the appendix. The histologic types include the following:[2]

Carcinoid tumor.

Well-differentiated neuroendocrine tumor.

Tubular carcinoid.

Goblet cell carcinoid.

Adenocarcinoid.

Atypical carcinoid.

Well-differentiated neuroendocrine carcinoma after resection (relevant to resection margins that are macroscopically involved by tumor).[2]

The only potential curative therapy for GI carcinoids, which may be possible in as many as 20% of patients, is resection of the primary tumor and local lymph nodes.[2,3,4] Endoscopic surgery may be suitable for some tumors depending on the location, number, size, and degree of malignancy.[4] Resection of nonhepatic tumor primaries is associated with increased median survival ranging from 69 to 139 months.[5,6] However, the extent of resection depends on the site of origin of a given tumor, the involvement of surrounding structures, and the extent of metastases.[1]

Somatostatin Analogues

The development of long-acting and depot formulations of somatostatin analogues has been important in the amelioration of symptoms of carcinoid syndrome. The result has been a substantial improvement in quality of life with relatively mild adverse effects.[1,7] The inhibitory effects of somatostatin on neurotransmission, motor and cognitive functions, smooth muscle contractility, glandular and exocrine secretions, intestinal motility, and absorption of nutrients and ions are mediated by cyclic adenosine monophosphate inhibition.[8,9] Experimentally, somatostatin has been shown to have a cytostatic effect on tumor cells. This effect involves hyperphosphorylation of the retinoblastoma gene product and G1 cell cycle arrest, in addition to somatostatin receptor (SSTR) subtype 3 [sst(3)]-mediated (and to a lesser extent, SSTR subtype [sst(2)]-mediated) apoptosis.[10,11,12] Somatostatin also appears to have some antiangiogenic properties.[1] However, only a small number of patients treated with somatostatin analogue therapy experience partial tumor regression.[1,4]

Currently available somatostatin analogues display high affinity for sst(2) and SSTR subtype 5, low affinity for SSTR subtype 1 and SSTR subtype 4, and medium affinity for sst(3). (Refer to the Somatostatin Receptor Scintigraphy section in the General Information About Gastrointestinal Carcinoid Tumors section of this summary for more information.) Octreotide, a short-acting somatostatin analogue and the first biotherapeutic agent used in the management of carcinoid tumors, exhibits beneficial effects that are limited to symptom relief, with about 70% of patients experiencing resolution of diarrhea or flushing. [1,4]

In the treatment of carcinoids, lanreotide, a long-acting somatostatin analogue administered every 10 to 14 days, has an efficacy similar to that of octreotide and an agreeable formulation for patient use.[13] The effects of lanreotide on symptom relief are comparable to those of octreotide, with 75% to 80% of patients reporting decreased diarrhea and flushing; however, there appears to be little improvement in tumor responses over shorter-acting octreotide.[1] Depot formulations include long-acting repeatable (LAR) octreotide and a slow-release depot preparation of lanreotide. One study comparing subcutaneous short-acting octreotide with monthly LAR octreotide reported an increased median survival from the time of metastatic disease diagnosis (143 months vs. 229 months in favor of the LAR form), representing a 66% lower risk for death among patients treated with the LAR formulation.[14] A randomized controlled study in metastatic midgut neuroendocrine tumors showed improved time to tumor progression with monthly LAR octreotide compared to placebo. (Refer to the Jejunal and Ileal carcinoids section in the Treatment Option Overview section of this summary.)

The typical duration of treatment with somatostatin analogues is approximately 12 months because of the development of tachyphylaxis (reported less frequently with long-acting formulations) and/or disease progression.[15,16,17] In the management of carcinoid crises, intravenous somatostatin analogues are effective; crises are usually precipitated by anesthesia, surgical interventions, or radiologic interventions.[18] Adverse effects of somatostatin analogue administration include:[19,20]

Biliary sludge and cholelithiasis occur in as many as 50% of the patients, but few patients (1%–3%) develop acute symptoms requiring cholecystectomy.[21]

Interferons

The most researched interferon in the treatment of carcinoid disease is interferon-alpha (IFN-alpha); comparable to somatostatin analogues, the most pronounced effects of IFN-alpha are inhibition of disease progression and symptom relief, with approximately 75% of patients reporting the resolution of diarrhea or flushing.[1] IFN-alpha, similar to other IFNs studied in the treatment of carcinoids (e.g., IFN-gamma and human leukocyte interferon), has substantial adverse effects, including alopecia, anorexia, fatigue, weight loss, fever, a flu-like syndrome, and myelosuppression; however, IFN-alpha may show greater antitumor activity than somatostatin analogues.[13] Both single-agent and multiagent chemotherapeutics appear to have little role in the management of these essentially chemoresistant tumors; no protocol has shown objective tumor response rates greater than 15%.[1]

Treatment of Hepatic Metastases

The management of hepatic metastases may include surgical resection; hepatic artery embolization; cryoablation and radiofrequency ablation (RFA); and orthotopic liver transplantation.[1] In one large review of 120 carcinoid patients, a biochemical response rate of 96% and a 5-year survival rate of 61% were reported for patients whose hepatic metastases were resected surgically.[22] The 5-year survival rate without surgical therapy is approximately 30%.[4] For hepatic artery embolization, the most frequently used single agent is gelatin powder; and, in more than 60 patients with carcinoid tumors, the use of gelatin powder resulted in 34% and 42% of patients achieving biochemical and tumor-diminution responses, respectively.[23,24,25] Trials using transcatheter arterial occlusion with chemoembolization have also been performed, with the most thoroughly researched combination involving hepatic artery ligation with gelatin foam and doxorubicin (4 trials and 66 patients), resulting in biochemical responses in 71% of patients and tumor regression in approximately 50% of patients.[1] However, the duration of response can be short lived after embolization, and embolization may be associated with adverse effects that range from transient symptoms (e.g., pain, nausea, fever, and fatigue), which occur in 30% to 70% of patients, to liver enzyme abnormalities, which occur in as many as 100% of patients (i.e., transaminitis and postembolization syndrome), to florid and potentially lethal carcinoid crisis with massive release of vasoactive substances.[4]

In one prospective trial, 80 RFA sessions were performed in 63 patients with neuroendocrine hepatic metastases (including 36 carcinoids), and 92% of the patients reported at least partial symptom relief. In the same 63 patients, 70% had significant or complete relief at 1 week postoperatively, with a perioperative morbidity of 5%; duration of symptom control was 11 ± 2.3 months, and median survival time was 3.9 years after the first RFA.[26] There are few trials of cryoablation of hepatic metastases, and the results of liver transplantation for metastatic disease are disappointing, reflecting the typically advanced disease states of transplant recipients.[1]

Information about ongoing clinical trials is available from the NCI Web site.

Radionuclides

The four radionuclide conjugates most commonly used in the treatment of carcinoid disease are 131I-MIBG (iodine-131-meta-iodobenzylguanidine), indium-111, yttrium-90, and lutetium-177, with the latter three bound to a variety of somatostatin analogues. However, the median tumor response rate for the patients treated with 131I-MIBG is less than 5%, although the modality appears somewhat more effective in achieving biochemical stability (~50%) or tumor stability (~70%).[1] Although 111In-labeled somatostatin analogues are the most commonly studied radiopeptides to date, largely reflecting their availability, and with therapeutic benefits similar to 131I-MIBG, the most promising advance in radiopeptide therapeutics has been the development of 177Lu-octreotate, which emits both beta and gamma radiation.[1] In the largest patient series treated to date with lutetium-labeled somatostatin analogues (n = 131; 65 with GI carcinoids), remission rates were correlated positively with high pretherapy octreotide scintigraphy uptake and limited hepatic tumor load.[27] In patients with extensive liver involvement, median time to progression was shorter (26 months) compared to patients who had either stable disease or tumor regression (>36 months).

Management of Carcinoid-Related Fibrosis

Bowel obstruction secondary to peritoneal fibrosis is the most common presenting symptom of small intestinal carcinoids. Heart failure secondary to right-sided valvular fibrosis represents a serious extraintestinal manifestation of carcinoid fibrosis and occurs in 20% to 70% of patients with metastatic disease; it accounts for as much as 50% of carcinoid mortality.[28,29] Currently, there is no effective pharmacologic therapy for either clinical problem. In the instance of bowel obstruction, surgical lysis of the adhesions often is technically demanding because of the cocoon-like effects of extensive fibrosis stimulated by the various tumor-derived growth factors.[30] Valvular replacement usually is required to manage carcinoid heart disease.[1]

Symptomatic Therapy

In addition to the use of long-acting depot formulations of somatostatin analogues as the principal agents in the amelioration of carcinoid symptoms, the nonspecific supportive care of patients includes:

Advising them to avoid factors that induce flushing or bronchospastic episodes including the following:

Diarrhea may be treated with conventional antidiarrheal agents such as loperamide or diphenoxylate; more pronounced diarrhea may be treated with the 5-HT receptor subtype 2 antagonist cyproheptadine, which is effective in as many as 50% of patients and may also help alleviate anorexia or cachexia in patients with a malignant carcinoid syndrome.[1]

Bronchospasm can be managed with theophylline or beta-2 adrenergic receptor agonists such as albuterol.[1]

Carcinoid crisis is manifested by profound flushing, extreme blood pressure fluctuations, bronchoconstriction, dysrhythmias, and confusion or stupor lasting hours or days and may be provoked by induction of anesthesia or an invasive radiologic procedure.[18,31] This potentially fatal condition can occur after manipulation of tumor masses (including bedside palpation), administration of chemotherapy, or hepatic arterial embolization.[32] In contrast with the treatment of other causes of acute hypotension, the use of calcium and catecholamines should be avoided in carcinoid crisis because these agents provoke the release of bioactive tumor mediators that may perpetuate or worsen the situation. Plasma infusion and octreotide are used for hemodynamic support. For the most part, the use of somatostatin analogues has replaced other pharmacologic maneuvers in the treatment of crises, and their use has been associated with increased survival rates. Prophylactic use of subcutaneous octreotide or the administration of a depot somatostatin analogue in a timely fashion before any procedures are undertaken is mandatory to prevent the development of a crisis.[1]

As might be expected, therapeutic approaches to GI carcinoids vary according to anatomical location. In 2004, a consensus statement regarding the diagnosis and treatment of GI neuroendocrine tumors (NETs) was published on behalf of the European Neuroendocrine Tumor Society (ENETS),[4] which details site-specific approaches to the treatment of GI carcinoids.

Gastric Carcinoids

Type I gastric carcinoids smaller than 1 cm are indolent with minimal risk for invasion and can be removed with endoscopic mucosal resection.[1,2,3] Local surgical excision may be performed for rare larger or invasive tumors, but exceptional cases with large multifocal lesions may require gastric resection. Follow-up with yearly endoscopic surveillance and repeated gastroscopy with multiple gastric biopsies is required, and treatment with somatostatin analogues may prevent recurrence.[4]

For type II carcinoids, surgery is focused on removing the source of hypergastrinemia, typically by excision of duodenal gastrinomas in patients with multiple endocrine neoplasia type I via duodenotomy with resection of lymph node metastases.[5,6,7] Because of their generally benign course similar to type I tumors, type II tumors can usually be managed with endoscopic resection (particularly for tumors <1 cm) followed by close endoscopic surveillance.[1,3] Liberal surgical excision or gastric resection with regional lymphadenectomy is performed for larger and multifocal tumors or for those with deep wall invasion or angioinvasion.[3] In patients with multiple tumors, somatostatin analogue treatment may be used to reduce tumor growth, particularly if hypergastrinemia has not been reversed by surgery.[4]

Sporadic type III gastric carcinoids, which behave more aggressively than type I and type II tumors, are treated with gastric resection and regional lymphadenectomy.[3] Tumors larger than 2 cm or those with atypical histology or gastric wall invasion are most appropriately dealt with by gastrectomy or radical gastrectomy.[1,8,9] Most of these tumors are metastatic at the time of presentation.[8] The 5-year survival may approach 50%, but, in patients with distant metastases, it is only 10%.[10,11]

Subtyping gastric carcinoids is helpful in the prediction of malignant potential and long-term survival and is a guide to management.[12] Based on a combined population from 24 Swedish hospitals, one study of 65 patients with gastric carcinoids (51 type I, 1 type II, 4 type III, and 9 poorly differentiated [designated as type IV in the study]), management varied according to tumor type. Among all of the patients, 3 received no specific treatment, 40 underwent endoscopic or surgical excision (in 10 cases combined with antrectomy), 7 underwent total gastrectomy, and 1 underwent proximal gastric resection; radical tumor removal could not be performed in 2 of 4 patients with type III and 7 of 9 patients with poorly differentiated tumors. (Refer to the Cellular and Pathologic Classification of Gastrointestinal Carcinoid Tumors section of this summary for more information.) Five- and 10-year crude survival rates were 96.1% and 73.9%, respectively, for type I tumors (not different from the general population) but only 33.3% and 22.2% for poorly differentiated gastric NETs.[12][Level of evidence: 3iiD].

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Duodenal Carcinoids

Duodenal carcinoids are rare, and there is no consensus on the optimal extent of surgical treatment.[1] In a retrospective review of 24 patients with a pathologic diagnosis of duodenal carcinoid tumor, most tumors (89%) measured smaller than 2 cm in diameter, and most (85%) were limited to the mucosa or submucosa. Lymph node metastases were identified in surgical specimens in 7 (54%) of 13 patients in whom lymph nodes were examined, including 2 patients with tumors smaller than 1 cm, which were limited to the submucosa. At a mean follow-up of 46 months, the disease-specific survival rate was 100%, and only 2 patients had recurrences in regional lymph nodes. No patient was reported to have distant metastases or the carcinoid syndrome.[1][Level of evidence: 3iiB] The authors of this study concluded that, although duodenal carcinoids are indolent, the presence of regional lymph node metastases cannot be predicted reliably on the basis of tumor size or depth of invasion, and their impact on survival is unclear.

In general, endoscopic excision of primary duodenal carcinoids appears to be most appropriate for tumors smaller than 1 cm.[1] Duodenal carcinoids smaller than 2 cm may be excised locally; for tumors between 1 cm and 2 cm, complete resection is ensured by operative full-thickness excision.[1,2] Follow-up endoscopy is indicated. Tumors larger than 1 cm may be difficult to remove completely endoscopically and should be evaluated with endoscopic ultrasonography before endoscopic resection is attempted because of their potential to invade beyond the submucosa.[3]

Appropriate management of tumors larger than 2 cm can be problematic.[2] However, in general, these tumors can be treated with operative full-thickness excision and regional lymphadenectomy. Lymphadenectomy is performed even in the face of negative preoperative imaging because of the high rate of lymph node metastasis for these tumors.[1]

In addition, some authors recommend that for tumors larger than 2 cm, a regional lymphadenectomy includes the lymph nodes in the following locations:

Posterior to the duodenum and pancreatic head and anterior to the inferior vena cava.

Regardless of the size of the primary tumor, abnormal lymph nodes detected on pretreatment imaging studies or at the time of surgery should be resected. Because little is known about the natural history of unresected, grossly evident lymph node metastases, nonoperative management might otherwise be supported. Node-positive patients should undergo continued radiographic surveillance regardless of the size of the primary tumor.[1]

Ampullary and periampullary duodenal carcinoids deserve special consideration because they differ clinically, histologically, and immunohistochemically from carcinoid tumors that occur elsewhere in the duodenum.[5] Although their rarity precludes the establishment of any definitive natural history, these tumors appear to behave unpredictably and might be viewed as a distinct category of carcinoid tumor when treatment options are being considered.[2] Compared to tumors in other duodenal sites, even small (<1 cm) ampullary and periampullary carcinoid tumors exhibit distinctly different aggressive behavior, and they may metastasize early.[5,6]

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Jejunal and Ileal Carcinoids

At the time of diagnosis, 58% to 64% of patients with carcinoids of the small intestine have metastatic disease in the regional lymph nodes or the liver.[1] Early surgical treatment should include removal of the mesentery by wedge resection and resection of lymph node metastases surrounding the mesenteric artery and vein to preserve intestinal vascular supply and to limit the intestinal resection.[2] With grossly radical tumor resections, patients may remain symptom free for extended periods of time; however, because of the tenacity of carcinoid tumors, patients should undergo lifelong surveillance.

Surgical treatment for advanced carcinoids involves prophylactic removal of mesenteric metastases early on because later the disease may become impossible to manage surgically.[3] Repeat surgery may be necessary if mesenteric metastases are left during primary surgery or have progressed after primary surgery.[2] These operations are difficult because of fibrosis between regions of the intestine, and surgery may result in fistulation, intestinal devascularization, or creation of a short bowel.[3] In patients with inoperable metastatic disease, 5-year survival is approximately 50% for those with inoperable liver metastases and approximately 40% for those with inoperable liver and mesenteric metastases.[4,5]

The effect of octreotide (long-acting repeatable, 30 mg intramuscularly every 28 days) on time to tumor progression in patients with metastatic midgut neuroendocrine tumors has been tested in a randomized, placebo-controlled clinical trial.[6] Although the planned study accrual was 162 patients, because of slow accrual, it was stopped after 85 evaluable patients were enrolled. At an interim analysis, the median time to tumor progression was 14.3 months in the octreotide group versus 6 months in the placebo group (HR = 0.34; 95% CI, 0.20–0.59; P < .0001). Quality of life was similar in both treatment groups. There was no difference in overall survival, but about three-quarters of the control group received octreotide at disease progression.[6][Level of evidence: 1iDiii].

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Appendiceal Carcinoids

Approximately 90% of appendiceal carcinoids measure smaller than 1 cm and are not located in the appendiceal base; these tumors can be consistently cured by appendectomy.[1]

Appendiceal carcinoids larger than 2 cm require right-sided hemicolectomy and ileocecal lymphadenectomy because of the significant risk of metastasis.[1] For tumors measuring 1 to 2 cm, treatment is controversial, but hemicolectomy may be appropriate if there is invasion in the mesoappendix, if there is residual tumor in the resection margins, or in the presence of lymph node metastases. For same-size lesions confined to the appendiceal wall, appendectomy alone may carry a low risk for metastases. Acceptable indications for hemicolectomy may include operative specimens that show high proliferative activity (high Ki67 index), high mitotic index, or signs of angioinvasion, but evidence is limited and histologic parameters for risk evaluation in appendiceal carcinoids measuring 1 cm to 2 cm requires definition.[1,2,3] Follow-up should be considered in patients for whom elevated serum chromogranin A may indicate the need for extended operation. Although survival is excellent with locoregional tumor, 10-year survival is approximately 30% with distant metastases.[1]

Goblet cell carcinoid or adenocarcinoid is a rare variant of appendiceal carcinoid with mixed endocrine and exocrine features.[1] Often presenting with a diffusely inflamed appendix and occurring in patients at a later age (approximately 50 years), these tumors are aggressive, often with peritoneal and ovarian metastases, and occasionally appearing as mucinous adenocarcinoma.[2,3,4] They do not express somatostatin receptors and cannot be visualized by 111-Indium octreotide scintigraphy. Goblet cell carcinoids are treated with right-sided hemicolectomy and lymphadenectomy in combination with chemotherapy. For disseminated tumors, aggressive surgical reduction including peritonectomy and oophorectomy may be required.[1] Goblet cell carcinoids have a 10-year survival rate of approximately 60%.[2]

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Colonic Carcinoids

Colonic carcinoids are often exophytic and large (>5 cm), but they rarely bleed. Only occasional right-sided lesions are positive with 111-Indium octreotide scintigraphy. Many of these tumors are aggressive with a high proliferation rate, and they often present with more liver metastases than regional lymph node metastases.[1] These tumors of the colon are treated similarly to adenocarcinoma of the colon.[2] Attempts to achieve radical resection by hemicolectomy or subtotal colectomy with lymphadenectomy should be made, but frequently only debulking is possible. The overall 5-year survival rate is approximately 40% and is slightly worse than the survival rate for colon adenocarcinoma.[1]

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Rectal Carcinoids

In general, rectal carcinoids smaller than 1 cm can be safely removed by endoscopic excision.[1] Excised specimens should be examined histologically to exclude muscularis invasion.[2,3,4,5]

Tumors measuring 1 cm to 2 cm should be investigated by transanal endosonography or magnetic resonance imaging. Absence of muscularis invasion or regional metastases may justify local excision.[1] The outcome from treating a lesion between 1 cm and 2 cm is unclear. The metastatic risk is between 10% and 15%.[6] Some studies demonstrate no benefit with aggressive management whereas other studies have reported successful treatment with local or radical surgery.[2,7,8] Although it may be possible to recognize tumors with particular atypia and high mitotic index before embarking on radical surgery, the presence of muscularis invasion or regional metastases generally supports aggressive excision. Generally, the procedure is an anterior rectal resection with total mesorectal excision and regional lymphadenectomy. In patients with distant metastases, prognosis is generally poor with an overall 5-year survival rate of approximately 30%.[1]

A similar approach to that used for tumors measuring 1 cm to 2 cm is used in patients with tumors larger than 2 cm but with no metastasis. However, rectal carcinoids of 1 cm to 2 cm have a substantially higher metastatic risk, between 60% and 80%.[2,6,9,10] Invasion of the muscularis propria is common in these tumors and indicates a high metastatic potential.[11] Local resection is unlikely to benefit patient survival with metastatic disease, but it may provide local symptomatic relief.[12] Locoregional resection may control local symptoms and pelvic disease without improving survival.[13,14] Although studies are limited, and the numbers of tumors studied are consistently small, aggressive surgery has not been shown to improve the survival outcome in this group of patients.[11]

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized gastrointestinal carcinoid tumor and regional gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Metastatic Gastrointestinal Carcinoid Tumors

Although the definitive role of surgery in metastatic disease has not been established, conservative resections of the intestine, mesenteric tumors, and fibrotic areas may improve symptoms and quality of life substantially in patients with metastatic hepatic, mesenteric, and peritoneal carcinoids. If the condition of the patient is such that surgery is not a greater risk than the disease, the primary tumor should be resected to prevent an emergency presentation with obstruction, perforation, or bleeding.[1] Despite common acceptance that resection of at least 90% of the tumor burden is required to achieve palliation, approximately 60% of patients with surgery alone will experience symptom recurrence; the 5-year survival rate is between 35% and 80%, depending on the experience of the center.[2,3] Because treatment with somatostatin analogues can achieve similar rates of symptom relief with fewer adverse effects, in each patient the benefits of surgical treatment of gastrointestinal (GI) carcinoid tumors should be weighed carefully against the potential risks of an open exploration. Tumor debulking, however, may potentiate pharmacologic therapy by decreasing the secretion of bioactive substances.[4]

Management of hepatic metastases may include surgical resection; hepatic artery embolization; cryoablation and radiofrequency ablation; and orthotopic liver transplantation. (Refer to the Treatment of Hepatic Metastases section of the Treatment Option Overview section of this summary for more information.) Cytoreductive surgery for hepatic metastases from GI carcinoids can be performed safely with minimal morbidity and mortality resulting in regression of symptoms and prolonged survival in most patients.[5] In one large review that included 120 carcinoid patients, a biochemical response rate of 96% and a 5-year survival rate of 61% were reported for patients whose hepatic metastases were resected surgically.[6][Level of evidence: 3iiDii]

In the case of liver metastases, localization and resection of the primary tumor may be considered, even among patients in whom the primary neoplasm is asymptomatic. In a retrospective study involving 84 patients, 60 of whom had their primary neoplasm resected, the resected group had a greater median progression-free survival (PFS) of 56 months, compared with 25 months of PFS for the primary nonresected group (P < .001). Median survival time for the resected group was longer at 159 months when compared with 47 months for the nonresected group (P < .001).[7][Level of evidence: 3iiDii ]

Although the response of carcinoid tumors to external-beam radiation therapy is very limited, palliative radiation therapy has some efficacy for bone and brain metastases and in the management of spinal cord metastases.[4]

Treatment with single-agent chemotherapy or multiple-agent chemotherapy appears to be of little benefit in the management of GI carcinoids because no regimen has shown objective tumor response rates greater than 15%.[4]

Treatment with radionuclides such as 131I-MIBG and 177Lu-octreotate may be of benefit. (Refer to the Radionuclides section of the Treatment Option Overview section of this summary for more information.)

Somatostatin analogues and interferon-alpha are the primary agents used in the treatment of carcinoid syndrome. (Refer to the Somatostatin Analogues section and Interferons section of the Treatment Option Overview section of this summary for more information.) Management of the symptoms of carcinoid syndrome may also include dietary modification and the use of various antidiarrheal agents, antihistaminics for skin rashes, and theophylline or beta-2 adrenergic receptor agonists for bronchospasm. (Refer to the Symptomatic Therapy section of the Treatment Option Overview section of this summary for more information.)

Information about ongoing clinical trials is available from the NCI Web site.

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with metastatic gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Recurrent Gastrointestinal Carcinoid Tumors

The prognosis for any treated carcinoid patient with progressive or recurrent disease is poor. Deciding on further treatment depends on many factors, including previous treatment, site of recurrence, and individual patient considerations. Attempts at re-resecting slow-growing tumors (e.g., repeat or multiple liver resections) are worthy of consideration after extensive evaluation, since successful further reduction of tumor volume may provide long-term palliation. Recurrence at any single site may also be potentially resectable. Clinical trials are appropriate and should be considered when possible.

Information about ongoing clinical trials is available from the NCI Web site.

Current Clinical Trials

Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with recurrent gastrointestinal carcinoid tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

Changes to This Summary (06 / 01 / 2012)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

This summary is written and maintained by the PDQ Adult Treatment Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ NCI's Comprehensive Cancer Database pages.

About This PDQ Summary

Purpose of This Summary

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of gastrointestinal carcinoid tumors. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.

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